Many oxides in which a crystal structure is the simple Perovskike structure may be used as the material of the ferroelectric substance showing the self-generating polarization resulting in the piezoelectric characteristic, dielectric characteristic, pyroelectric characteristic, electric conductance characteristic, electrostrictive effect, and electro-optical effect, etc.
The ferroelectric substance having such properties may be adapted to an IC card as a semiconductor memory element, an actuator element including a piezoelectric pump structure through ultra-fine-process on a silicon substrate, and to a filter element for communication apparatus for detecting surface acoustic wave (SAW). Moreover, since such ferroelectric substance is an oxide, it has the property to transmit the light and is therefore applied to an optical switch element utilizing change in refractive index (electro-optical effect) which is generated when a voltage is applied thereto.
When the ferroelectric substance is adapted to a 1T/1C type memory element (one capacitance element corresponds to one transistor), it is expected to provide the ferroelectric substance structure which provides the maximum polarization by applying a voltage in the vertical direction of a semiconductor substrate. For this purpose, it is therefore preferable that the ferroelectric substance structure includes an oxide having the simple Perovskite structure of the tetragonal crystal phase in which the residual polarizing direction is aligned in the direction of plane (001).
An oxide having the simple Perovskite structure aligned to the plane (001) can be obtained with the epitaxial growth method. The film obtained by epitaxial growth can be suitably used in an electronic element including the ferroelectric substance film as the film which is aligned not only in the vertical direction to the substrate but also within the substrate.
Moreover, it is also required to suppress production of a silicon oxide film, even if the substrate is in contact with the heated raw material gas, in order to realize epitaxial growth of the desired ferroelectric substance film on the highly flexible silicon single crystal substrate. Therefore, such ferroelectric oxide film is provided on the silicon single crystal substrate using the Yttria-Stabilized Zirconia (hereinafter, referred to as YSZ), magnesium oxide, and magnesia spinnel or the like as the underlayer (See JP-A No. 110592/1997).
In addition, alignment property is controlled by providing a rare earth oxide such as CeO2 on the underlayer provided on the silicon single crystal substrate. (See JP-A No. 110592/1997), also see J. Appl. Phys. 66 (1989) 5826.